The invention relates to a rim or assembly of elements forming a rim for the mounting and travel of a tire without an independent inner tube, that is to say, a xe2x80x9ctubelessxe2x80x9d tire, which is intended more particularly for mounting on heavy vehicles.
If we consider the rims of rolling assemblies which are currently used, we can distinguish mainly between drop-center rims, having frustoconical seats which are inclined relative to the axis of rotation of the assembly by an angle of 5xc2x0 or 15xc2x0, and flat-based or practically flat-based rims having seats inclined at 0xc2x0 or at 5xc2x0 relative to the axis of rotation.
So-called drop-center rims comprise a mounting groove, the diameter of which is significantly less than the nominal diameter of the rim. This internal diameter of the rim is considered by users to be too small because it does not make it possible to select, for example, brake drums of dimensions suitable for effective braking of vehicles which are becoming ever more powerful relative to their weight.
Because of this, said rims are commonly used for mounting and travel, for example, of passenger-car and/or heavy-vehicle tires, but far less often, and sometimes not at all, for other types of vehicles, such as, for example, site machinery and construction machinery.
For mounting a xe2x80x9ctubelessxe2x80x9d tire, a flat-based rim requires the presence of at least one removable lateral ring, a locking ring and a gasket, and obviously the rim base provided with a fixed flange on the side opposite the side from which the parts are removable. Therefore at least three parts are required. In the majority of cases, the number of parts necessary is greater than three, and may sometimes be as many as six parts for large dimensions of tires. With the exception of the rubber gaskets, the parts of a rim are metal, and consequently heavy, bulky and difficult to handle. As a result, the fitting and removal of tires of large and very large dimensions are difficult, long operations. The positioning and/or removal of a wheel fitted with such a tire requires immobilization of the vehicle or machinery for a not inconsiderable period. Furthermore, the metal parts used, namely the conical rings, the flanges and the locking rings, are frequently subject to localized, partial wear, with or without oxidation and rusting, and this damage, during later use, results not only in defective mounting with loss of pressure, but also the creation of concentration of stresses which may result in breakage of parts. Moreover, as is known, the vulcanized rubber gaskets require great care in positioning; furthermore, they are subject to natural oxidation and poor storage conditions, hence the appearance of numerous cracks; thus, in many cases, the conditions are such that said gaskets do not satisfactorily fulfil the function for which they were intended.
In order to overcome the above disadvantages, to use the smallest possible number of parts and to ensure better connection of the rolling assembly to the wheel over time, the invention proposes a novel assembly for mounting a tire without independent inner tube, comprising at least two conical metal rings intended to receive the tire beads, said two metal rings being positioned and locked on the hub of the vehicle by means of two circular lateral locking rings, each being composed of a vulcanized rubber mix reinforced by and coating a reinforcement ring which is circumferentially elastic and radially resistant to compression, and being placed in a recess in the hub.
xe2x80x9cCircumferentially elastic reinforcement ringxe2x80x9d is to be understood to mean an element, the circumferential development of which is liable to be elongated by at least 3% under a force of at most 50 daN, and which returns to its initial state when the force is removed.
xe2x80x9cReinforcement ring radially resistant to compressionxe2x80x9d is to be understood to mean a ring, the maximum radial dimension of the cross-section, that is to say, the greatest radial distance between two points of the contour of said section which are located on a line perpendicular to the axis of rotation of the rim, of which is reduced by at most 2% under force.
xe2x80x9cConical mounting ringxe2x80x9d is to be understood to mean a ring having radially to the outside a seat, the generatrix of which forms a certain angle with the direction of the axis of rotation, but also a ring, the seat of which has a generatrix which forms a zero angle with said axis.
xe2x80x9cVulcanized rubber mixxe2x80x9d or xe2x80x9cvulcanized rubber compositionxe2x80x9d is to be understood to mean a mix of elastomer(s), reinforcing fillers and well-known additives which are vulcanized at a certain temperature. Preferably, the coating mix of the reinforcement ring will have a secant modulus of elasticity at a relative elongation of 10% of at least 6 MPa.
A circular rubber ring reinforced by a circular reinforcement ring, said ring being circumferentially elastic and radially resistant to compression, is described in U.S. Pat. No. 5,232,033. Said rubber ring, in the cited patent, is used as an adapter, that is to say, a means having a meridian section adapted so as to be able to mount tire beads having a given configuration on rims intended to receive beads of a different configuration. The ring thus used is a bead mounting ring with, in particular, a radially outer wall of meridian profile identical to the standardized profiles, when it is a tire which meets the current standards which is being mounted. The invention uses such a reinforced rubber ring in an adapted form, not as an adapter or mounting ring, but as a locking ring, the mounting rings, within the scope of the invention, being of metal and not of rubber.
A locking ring according to the invention is considered as having at least two walls: one radially inner wall and one radially outer wall, said two walls possibly being joined by lateral walls virtually perpendicular to the direction of the axis of rotation. The radially inner wall is of a shape which is similar to the shape or profile of the recesses or grooves formed on the hub of the machine in order to receive said rings. Said recesses, when viewed in meridian section, may be of any shape, but preferably have a meridian section, the surface of which is virtually triangular with a base on the generatrix of the hub and with two sides forming acute angles which may be between 10xc2x0 and 45xc2x0 with the direction parallel to the axis of rotation, the two sides being joined opposite said base by a rounded apex, in order to minimize the concentrations of stresses and the risk of cracking due to fatigue. The virtual height of said triangle, lowered by the rounded apex on said base, is preferably between 10 and 45 mm. The radially inner wall of the locking ring, in meridian section, has a profile identical to the inner profile of the virtual triangle above.
The meridian section of the reinforcement ring of the locking ring, in its radially inner part, may be of any shape insofar as a major part of the maximum radial dimension of its meridian section lies within the triangular section of the recess formed in the hub. xe2x80x9cMajor partxe2x80x9d is to be understood to mean a radial distance equal to at least 25% of the maximum radial dimension of the section of the reinforcement ring. Said radially inner part of the reinforcement ring may have two preferred shapes: elliptical (the circle being considered as an ellipse) and polygonal with at least two sides substantially parallel to the two sides of the triangular section of the recess of the hub, which permits correct positioning of the elastic locking ring and allows said positioning to be maintained despite the forces or stresses which arise upon inflation, loading and travel of the tire.
As for the meridian section in the radially outer part of the locking ring, it may also be elliptical in shape, but will preferably be composed of at least one frustoconical part, the generatrix of which forms an angle which may be between 15xc2x0 and 35xc2x0 with the direction of the axis of rotation. Said frustoconical part, upon mounting of the tire, will come to be opposite the frustoconical part of the radially inner wall of the conical ring on which the tire bead will be mounted. The meridian section of the reinforcement ring, in its radially outer part, may then be elliptical, circular or polygonal with, in the latter case, one side parallel to the frustoconical part of the radially outer wall of the ring.
Whatever the form of the meridian section of the reinforcement ring, the latter is advantageously an annular spring with adjacent metal coils. An individual coil may have any cross-section, but it is preferably circular, and the diameter of the cross-section of the coil, depending on the dimensions of the spring, is between 2 and 8 mm, which permits deformation of the coil under compressive force of less than 2%. The reinforcement ring may also be a succession of cylindrical elements of rigid material, such as steel, or ceramic, said elements being of a length less than the diameter of the cylinder and joined together circumferentially by a rubber mix of high Shore A hardness.
In the case in which a spring is used, the compressive strength of said spring may advantageously be improved by inserting within the coils either a continuous circular element of vulcanized rubber of high Shore A hardness, or a continuous circular element of plastics material, said elements being circularly discontinuous in order to maintain the elasticity of the spring.
Said spring, in order to facilitate the operations of demounting the tire and removing the locking ring, is provided with a cord or metal strap which makes it possible to dislodge the ring from the recess in the hub by means of a tensile stress exerted on said cord.
The metal mounting ring is a metal element composed of a rim seat, which is generally frustoconical although it may be cylindrical, or other, said seat being extended axially and radially to the outside by a rim flange, said flange possibly being independent of the seat and being removable relative to said seat. Said ring has a radially inner wall formed of at least one frustoconical part, the generatrix of which forms an angle of between 15xc2x0 and 35xc2x0 with the direction of the axis of rotation, whereas the radially outer wall, viewed in meridian section, is composed firstly of a frustoconical generatrix forming an angle which may be between 0xc2x0 and 16xc2x0 with the direction of the axis of rotation, and, secondly, extending said generatrix axially to the outside by means of an arc of a circle of the curve representing the axially inner and radially outer profile of the rim flange. Said curve in all cases is advantageously located radially to the outside and axially to the inside of a straight-line segment joining the point of intersection of said curve with the frustoconical generatrix above and that point of said curve which is farthest from the axis of rotation. Thus, said curve may be formed of an arc of a circle which is at a tangent to the arc of a circle connecting the frustoconical generatrix and the curve. It may also be formed of a straight-line segment whether or not perpendicular to the axis of rotation, which is at a tangent radially to the inside to the above connecting arc and radially to the outside to a second arc of a circle so as to obtain the desired curve. The metal mounting rings may be independent of the tire and more particularly of the beads of said tire. So as to facilitate and accelerate the mounting and demounting operations, as well as the various handling operations, the conical rings with seats and flanges form an integral part of the tire in the same way, for example, as the bead wires; said rings may be rendered integral with the beads of the tire by a press-fitting without any possibility of detachment. Such a principle is described in U.S. Pat. No. 3,913,653.
Whether or not integral with the beads of the tire, and in order to permit easier handling of the elements which are to be positioned, the metal bead mounting rings are advantageously provided in their axially inner parts with an air-cushion system, which makes it possible to have and to maintain a free space between the hub and the radially inner part of the rings during the mounting operations, which results in greatly improved axial displacement. Said free space of 5 to 20 mm is also intended to permit engagement by sight on the hub without squeezing the tire/metal ring assembly.
The invention is more fully described with reference to non-limitative embodiments which are illustrated in the accompanying drawings.